// http://jsfiddle.net/9zxvE/

// Opera 8.0+
var isOpera = !!(window.opera && window.opera.version);
// FF 0.8+
var isFirefox = testCSS('MozBoxSizing');
// At least Safari 3+: "[object HTMLElementConstructor]"
var isSafari = Object.prototype.toString.call(window.HTMLElement).indexOf('Constructor') > 0;
// Chrome 1+
var isChrome = !isSafari && testCSS('WebkitTransform');
// At least IE6
var isIE = /*@cc_on!@*/false || testCSS('msTransform');

function testCSS(prop) {
    return prop in document.documentElement.style;
}